This invention relases in general to emergency locking safety belt retractor mechanisms for use in adjustably anchoring safety belts and/or harness assemblies employed for restraining passengers in vehicle seats during emergency operations. More particularly, the present invention relates to webbing tension relieving devices, for limiting the tension applied to the safety belt webbing by the storage reel bias spring. Such tension, unless relieved, may be a source of discomfort to occupants of the vehicle during the use of the safety belt webbing system and in some automatic locking retractors may result in a cinching effect known in the art and hence may lead the occupants of the vehicle to avoid using the safety belt system.
Previous efforts to obtain a tensionless effect for safety belt webbing in vehicle associated safety belt retractors have required positive action by the occupant in order to engage the tensionless feature. An example of these previous efforts may be found in Heath, U.S. Pat. No. 3,834,646. The Heath patent requires the occupant to first protractively extend the seat belt webbing then allow retraction of the seat belt webbing followed by a further protractive movement of the seat webbing. This required manipulation of the belt may allow some users to circumvent the available tensionless feature should he be in a hurry and, therefore, should the occupant find the tension applied to the safety belt webbing by the webbing storage reel bias spring objectionable, the occupant might indeed neglect to fasten the seat belt at all.
In some automatic locking retractors in use heretofore, a loose or slack condition of the webbing is prevented during occupant movement by the retraction spring winding in such slack as it occurs, with the automatic locking retractor locking the webbing in shorter and shorter length, as the user moves about in his seat until an uncomfortable result is achieved known in the art as a "cinching" effect.
Additionally, it should be noted that other prior efforts to achieve a tensionless mode of operation, thereby avoiding the cinching effect, have potentially resulted in the creation of a loose-loop condition when the occupant extends the belt beyond the point where a snug fit of the belt would otherwise occur and then engages the tensionless mechanism. This loose-loop condition, although it might be ultimately comfortable for the occupant, creates a most dangerous condition for the occupant as it allows a zone of free travel by the occupant during an emergency condition. The potential for increased injury to the occupant is therefore greatly increased.
It has heretofore been recognized that an improved webbing tension relieving mechanism for relieving the tension applied to the safety belt webbing by the webbing storage reel bias spring is needed. It is further recognized that such tension relieving mechanism optimally would be automatically engaged by a simple protractive movement of the seat belt webbing by the occupant during buckle-up, allow for occupant movement without a cinching effect and be automatically resetting when the occupant resumes a normal position of use. In addition to the desirability of such a low tension feature a means for providing a low tension limited travel of the belt after buckle-up is highly desirable to allow for minor occupant movements.